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ABSTRACT Observations of reionization-era analogues at z ∼ 3 are a powerful tool for constraining reionization. Rest-ultraviolet observations are particularly useful, in which both direct and indirect tracers of ionizing-photon production and escape can be observed. We analyse a sample of 124 z ∼ 3 galaxies from the Keck Lyman Continuum Spectroscopic Survey, with sensitive spectroscopic measurements of the Lyman continuum region. We present a method of removing foreground contamination from our sample using high-resolution, multiband Hubble Space Telescope imaging. We re-measure the global properties of the cleaned sample of 13 individually detected Lyman continuum sources and 107 individually undetected sources, including a sample-averaged absolute escape fraction of fesc, abs = 0. 06 ± 0. 01 and a sample-averaged ratio of ionizing to non-ionizing ultraviolet flux density of 〈f900/f1500〉out = 0. 040 ± 0. 006, corrected for attenuation from the intergalactic and circumgalactic media. Based on composite spectra, we also recover a strong positive correlation between 〈f900/f1500〉out and Lyα equivalent width (Wλ (Ly) ) and a negative correlation between 〈f900/f1500〉out and UV luminosity. As in previous work, we interpret the relationship between 〈f900/f1500〉out and Wλ (Ly) in terms of the modulation of the escape of ionizing radiation from star-forming galaxies based on the covering fraction of neutral gas. We also use a Wλ (Ly) -weighted 〈f900/f1500〉out to estimate an ionizing emissivity from star-forming galaxies at z ∼ 3 as ϵLyC ≃ 5. 5 × 1024 erg s−1 Hz−1 Mpc−3. This estimate, evaluated using the uncontaminated sample of this work, affirms that the contribution of galaxies to the ionizing background at z ∼ 3 is comparable to that of active galactic nuclei.
Pahl et al. (Fri,) studied this question.